Fuel pump HELP

weezall97

New Member
Aug 1, 2019
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0
1
52
Rocky Mount Va
Been on vacation but need help 02 mustang gt 4.6 no power going to fuel pump have got 12 volts at inertia switch.Can connect ground wire and hot wire to fuel pump and it works Anybody have idea of what it migjt be fuse is good Please let me know what you think
 
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08GT500

Active Member
Jul 12, 2018
384
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Massachusetts
Hi,
Car’s starter turns the Car motor over strong?
Posted a few pics below of the circuits so you know what you’re testing. Note the 20A fuse under the Hood.
!!Please post if engine turns over ok with key, or not. Also, if the pump primes as it should.!!
Have a few questions with some initial (vague) tests to attempt, meanwhile. Will help narrow it down .
1) How did this issue present itself? Did you let it sit for a few days or longer and the vehicle didn’t start, etc? Last thing that occurred prior to failure?
2) When you turn the key, does the fuel pump start running for about 7 seconds? (Prime). This should rule out a CCRM issue.
3) Do you have a factory or aftermarket Security system installed, have you noted a Security light at any point?
4) Check for 12VDC at both connections on the inertia switch, using a clean chassis area for grounding the VOM’s other lead (Wires Pink & Green, diagram #1). May also temporary jumper the 2 wires.
5) Check for power at the Plug going to the fuel pump with your VOM, use a clean area of Chassis with VOM on DCV. Someone needs to turn key to on so power for pump prime is present....Piercing the wires Insulation with Pins, tape both to affix, do NOT let them touch each other or Ground when testing! Check with VOM.
Ground, or power is missing, check connector pins for corrosion. Not rocket science, but can be irritating.
...... Verify Ground is present at the connector, use other lead to a clean Chassis area for Ground. VOM on audible continuity.
- Use a helper to cycle the key to turn on for pump prime.-
6) Check what battery voltage you have at the terminals, should be about 12.5-13.8V. Add a charger overnight after verifying your Grounds. Ground to block, block to Chassis, battery to Chassis, battery to CPU.
7) Is there anything else in the vehicle that does not function? Is the Car a Convertible?
8) Re-Check all your fuses. Under dash, underhood fuse shown using a VOM on each of the (2) steel pieces protruding through each fuse, so fuses need not be removed.
Find good Chassis ground. Test, and affix VOM lead in place. Start checking both ends of fuses with VOM on DCV. No power at either end, switch VOM to Confinuity & test with VOM leads across both ends of metal.protruding through tops of de-energized Fuse(s). (Diagrams below)..
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9) Have many keys on your ring? ignition switches are not meant to carry 10 keys. Try cycling the Key several times to see if you can get the pump to run for the initial prime.
If you have tilt steering, try readjusting..
10) Follow the wiring from the pump to the CCRM up front, look for damaged wiring, poor connections.
-Hopefully something less expensive, FYI: Fuel Pump relay is located in the CCRM, The CCRM is located on the passenger side fender under the hood near the air cleaner assembly. It is replaced as a unit, unless you’re comfortable enough to disassemble.
You may be able to find a used CCRM if that turns out to be the culprit, will be easier with your feedback, once posted.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,388
422
164
Houston Texas
FYI. For the 1999-2004 model year using a FPDM there isn't supposed to be actual power going to the fuel pump except when:
  • during initial key on "prime" for a few seconds.
  • when the PCM senses that the motor has actually started.
IF you are expecting to see power at the fuel pump all the time, this is not correct. Also, the output of the FPDM is a pulsed DC duty cycle. Not all VOM meters can read this correctly.

1996+ Crank with no start check list

Note, IF there is confirmed key on +12 at the trunk IFS switch, then the CCRM is likely good. However it can never hurt to verify there isn't excessive voltage drop to the trunk IFS switch.

Howto perform charging system voltage drop test

Or confirm that the voltage at the trunk IFS switch remains close to battery voltage during cranking.
 

weezall97

New Member
Aug 1, 2019
16
0
1
52
Rocky Mount Va
FYI. For the 1999-2004 model year using a FPDM there isn't supposed to be actual power going to the fuel pump except when:
  • during initial key on "prime" for a few seconds.
  • when the PCM senses that the motor has actually started.
IF you are expecting to see power at the fuel pump all the time, this is not correct. Also, the output of the FPDM is a pulsed DC duty cycle. Not all VOM meters can read this correctly.

1996+ Crank with no start check list

Note, IF there is confirmed key on +12 at the trunk IFS switch, then the CCRM is likely good. However it can never hurt to verify there isn't excessive voltage drop to the trunk IFS switch.

Howto perform charging system voltage drop test

Or confirm that the voltage at the trunk IFS switch remains close to battery voltage during cranking.
The car sit for a while here is what I have done When I crank car the. Inertia switch has 12 volts on both wires the connectors are clean a new pump and I checked before putting on car plus i can run hot and ground to pump from battery and it comes on and stays on when i turn key on I have 5 volts at fuel pump car will start for few seconds if I spray starting fluid in throttle body
 

wmburns

SN Certified Technician
Aug 14, 2009
5,388
422
164
Houston Texas
You didn't answer the question about IF the fuel pump "primes" at initial key on.

Are you positive that the correct fuel pump was used for THIS application? There is a difference between the fuel pump used in a return style verses a return-less fuel system. A fuel pump for a return style fuel system will not give good service in a return-less style system.

I'm assuming that the 5 volt is what you are measuring between the FPDM and the fuel pump itself. Seeing only 5 volts isn't necessarily a problem. As stated before not every VOM is able to correctly read a DC pulse width wave form.

When do you see the 5 volts at the fuel pump? At initial key on? Does the 5 volts go away after a few seconds?

If asking for me to handicap this thread, here's my guess. IF the fuel pump does NOT prime at initial key on, then incorrect fuel pump has been used such that it won't start under pulse width DC power of the FPDM.

What does the PCM "think" is the fuel pressure is?
 
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